1. Field of the Invention
This invention relates to a device which corrects a focused image tremble of an optical device due to hand tremble and so on.
2. Description of the Related Art
Conventionally, there are some optical devices, for example a camera, which are provided with a focused image tremble correcting device for correcting a focused image tremble due to a hand tremble and so on. The applicant suggests a correction optical system driving mechanism in the Japanese Unexamined Patent Publication (Kokai) No.6-35022 or in the U.S. Pat. No. 5,305,040. The driving mechanism moves a correction optical system, which forms an imaging optical system with other optical systems, on a plane perpendicular to the optical axis of the correction optical system. The driving mechanism moves the correction optical system in a direction on the plane such that the focused image tremble can be canceled. Namely, the tremble is corrected by moving the correction optical system on the above-mentioned plane such that trembles of the imaging optical system in two directions crossing at right angles (the vertical direction and the horizontal direction) can be canceled.
In the driving mechanism suggested in the above-mentioned publication, the correction optical system is rotated along the above-mentioned plane in order to simplify the mechanical structure so that the correction optical system can be driven using a small amount of power. The driving mechanism has a structure described below.
A first rotating board is mounted on a fixed board which is fixed in the optical device, being rotatable around a first rotating shaft. A second rotating board is mounted on the first rotating board, being rotatable around a second rotating shaft. A lens supporting member, which supports the correction optical system, is provided in such a manner that the lens supporting member penetrates through the fixed board, and the first and second rotating board. The first and second rotating shafts are situated so as to be parallel to the optical axis of the correction optical system. The first and second rotating boards are respectively rotated by corresponding driving machines.
In this correcting device, as described in the above-mentioned publication, the amounts of rotation of the rotating boards are calculated based on a linear-approximation. Namely, the linear moving component of the focused image in the horizontal direction is canceled by the displacement of the first rotating board in the horizontal direction defined by the rotation of the first rotating board, and the linear moving component of the focused image tremble in the vertical direction is canceled by displacement of the second rotating board in the horizontal direction defined by the rotation of the second rotating board.
As described above, the amount each of the first and second rotating boards is driven in either the horizontal and vertical directions is controlled by the corresponding amount of rotation of the first and second rotating boards, which is calculated by using linear-approximation, with respect to each of the linear moving components of the focused image in the horizontal and vertical directions. In other words, the tremble correction is carried out by assigning an amount of rotation of one rotating board to one linear moving component. In this specification, this driving control is referred to as xe2x80x9cpseudo-linear movementxe2x80x9d.
However, in this mechanism, if the distance between the rotating shafts and the optical axis of the correction optical system is set short to reduce the size of the device, the error in the linear-approximation is amplified, and the accuracy of the amount each rotating board is driven is lowered.
Further, the second rotating board is mounted on the first rotating board, and the pseudo-linear movement is carried out with respect to each of the first and second rotating boards. Accordingly, with respect to one rotating board, the pseudo-linear movement is performed without considering an error generated by rotating the other rotating board, and further with respect to the other rotating board, the pseudo-linear movement is performed without considering the error generated by rotating the first rotating board. Therefore, the total error is amplified.
Accordingly, it is difficult to compact the focused image tremble correcting device, so that the overall size of the optical device cannot be reduced. Namely, though the optical device is required to be small from the viewpoints of manipulation and portability, such requirement cannot be achieved.
Therefore, an object of the present invention is to provide a focused image tremble correcting device which is simple and small, and further accurately corrects a focused image tremble.
In accordance with an aspect of the present invention, there is provided a focused image tremble correcting device comprising: a tremble detector that detects a tremble of an optical device; a correction optical system that is included in an imaging optical system of the optical device and corrects the tremble; a fixed member that is fixed in the optical device; a first rotating member that is supported on the fixed member and rotates the correction optical system around a first rotating axis which is parallel to an optical axis of the correction optical system; a second rotating member that is supported on the first rotating member and rotates the correction optical system around a second rotating axis which is parallel to the optical axis of the correction optical system; and a controller. The controller calculates a moving component for an object image in a first linear direction on a focal plane of the imaging optical system. The moving component is due to an angular tremble of the optical axis of the imaging optical system. The calculation is based on the result of the tremble detector. Further, the controller cancels the moving component in the first linear direction by controlling rotations of both the first rotating member and the second rotating member.
Preferably, the controller further calculates a moving component in a second linear direction on the focal plane, and calculates a rotational angle for each of the first and second rotating members in order to control both the first and second rotating members such that both the moving component of the object image in the first linear direction and the moving component of the object image in the second linear direction can be canceled. The first and second linear directions cross on the focal plane.
Optionally, the first linear direction and the second linear direction cross at right angles, and the intersection point of the first and second linear direction corresponds to an intersection point of the optical axis of the imaging optical system and the focal plane.
Preferably, the controller calculates the rotational angles of the first and second rotating members such that the moving component in the first linear direction, the moving component in the second linear direction, the rotational angle of the first rotating member, and the rotational angle of the second rotating member satisfy the formulas to follow.
x=K1xc3x97(L2xc3x97Cos(xcex4+xcex8+xcex12)+L1xc3x97Sin(xcex11+xcex8)) 
y=K2xc3x97(L2xc3x97Sin(xcex4+xcex8+xcex12)xe2x88x92L1xc3x97Cos(xcex11+xcex8)+d1) 
(herein, x: moving component of the object image in the first linear direction,
y: moving component of the object image in the second linear direction,
K1: predetermined proportional coefficient,
K2: predetermined proportional coefficient,
L1: length of a straight line which connects the intersection point of the first rotating axis and the focal plane with the intersection point of the second rotating axis and the focal plane,
L2: length of a straight line which connects the intersection point of the optical axis of the correction optical system and the focal plane with the intersection point of the second rotating axis and the focal plane,
xcex8: rotational angle of the first rotating board,
xcex4: rotational angle of the second rotating board,
xcex11: an angle when the second linear direction is rotated in the clockwise direction to a straight line which connects the intersection point of the first rotating axis and the focal plane with the intersection point of the second rotating axis and the focal plane, around the intersection point of the first rotating axis and the focal plane,
xcex12: an angle when the first linear direction is rotated in the clockwise direction to a straight line which connects the intersection point of the optical axis of the imaging optical system and the focal plane with the intersection point of the second rotating axis and the focal plane, around an intersection point of the first linear direction and the second linear direction,
d1: distance between the intersection point of the first rotating axis and the focal plane and the intersection point of the optical axis of the imaging optical system and the focal plane)
optionally, when the optical axis of the correction optical system is coaxial with an optical axis of other optical systems included in the imaging optical system, a straight line, which connects an intersection point of the first rotating axis and a plane perpendicular to the optical axis of the correction optical system with an intersection point of the optical axis of the correction optical system and the perpendicular plane, and a straight line, which connects an intersection point of the second rotating axis and the perpendicular plane with an intersection point of the optical axis of the correction optical system and the perpendicular plane, do not cross at right angles.
Preferably, the focused image tremble correcting device further comprises: a first driving mechanism including: a first driving member for rotating the first rotating member around the first rotating axis; and a first urging member for urging the first rotating member to the first driving member; and a second driving mechanism including: a second driving member for rotating the second rotating member around the second rotating axis; and a second urging member for urging the second rotating member to the second driving member.
For example, the first driving member is a stepping motor which is fixed on said fixed member; the first urging member is a coil spring, one end of which is fixed on the fixed member and the other end of which is fixed on the first rotating member; the second driving member is a stepping motor which is fixed on the first rotating member; and the second urging member is a coil spring, one end of which is fixed on the first rotating member and the other end of which is fixed on the second rotating member.
Preferably, the focused image tremble correcting device further comprises: a first supporting mechanism that includes: a first pivot shaft, the rotating axis of which is the first rotating axis, the first pivot shaft being fixed on the first rotating member, and one end of the first pivot shaft being in contact with a first bearing which is provided on the fixed member; a first elastic member, being flat, that is provided with a second bearing with which the other end of the first pivot shaft is in contact; and a first supporting element, being fixed on the fixed member, that supports the first elastic member in such a manner that an elastic power of the first elastic member is applied to the first pivot shaft at all times such that the first pivot shaft is urged to the fixed member; and a second supporting mechanism that includes: a second pivot shaft, the rotating axis of which is the second rotating axis, the second pivot shaft being fixed on the second rotating member, and one end of the second pivot shaft being in contact with a third bearing which is provided on the first rotating member; a second elastic member, being flat, that is provided with a fourth bearing with which the other end of the second pivot shaft is in contact; and a second supporting element, being fixed on the first rotating member, that supports the second elastic member in such a manner that the elastic power of the second elastic member is applied to the second pivot shaft at all times such that the second pivot shaft is urged to the first rotating member.
More preferably, the one end and the other end of the first pivot shaft are cone-shaped, the first bearing of the fixed member and the second bearing of the first elastic member are tapered, the first pivot shaft is positioned in such a manner that the one end of the first pivot shaft is abutted against the center of the first bearing and the other end of the first pivot shaft is abutted against the center of the second bearing, the one end and the other end of the second pivot shaft are cone-shaped, the third bearing of the first rotating member and the fourth bearing of the second elastic member are tapered, the second pivot shaft is positioned in such a manner that the one end of the second pivot shaft is abutted against the center of the third bearing and the other end of the second pivot shaft is abutted against the center of the fourth bearing.
According to the present invention, in the focused image tremble correcting device which rotates the correction optical system around two different axes, the moving component of the object image in the first linear direction on the focal plane, due to the angular tremble of the optical axis of the imaging optical system, is canceled by rotating both the first rotating board and the second rotating board. Accordingly, accurate correction of the focused image tremble can be carried out at all times.
Further, the mechanism according to the present invention cancels the displacement of the object image by combining the rotations of two rotating boards. Accordingly, it is not necessary to make the distance between the first rotating axis and the correction optical system large and nor is it necessary to make the distance between the second rotating axis and the correction optical system large, in order to heighten the accuracy of the correction. Namely, the overall size of the optical device can be small.
When the first rotating board is supported on the fixed member by the elastic power of the first elastic member which is flat, the position of the first rotating board is accurately held in the direction along the optical axis of the correction optical system. Similarly, when the second rotating board is supported on the first rotating board by the elastic power of the second elastic member which is flat, the position of the second rotating board is accurately held in the direction along the optical axis of the correction optical system. Namely, the planes of the first and second rotating boards are prevented from tilting with respect to the optical axis, so that the correction of the focused image tremble is stably carried out.
Further, when both ends of the first pivot shaft are cone-shaped and the bearings of the fixed member and the first elastic member are tapered, and the first pivot shaft is positioned such that both ends are abutted against the center of the corresponding bearings, the rotational friction of the first rotating board is reduced. Accordingly, the first rotating board can be smoothly rotated, so that controlling the amount the first rotating board is driven can be accurately carried out.
Similarly, when both ends of the second pivot shaft are cone-shaped and the bearings of the first rotating board and the second elastic member are tapered, and the second pivot shaft is positioned such that both ends are abutted against the center of the corresponding bearings, the rotational friction of the second rotating board is reduced. Accordingly, the second rotating board can be smoothly rotated, so that controlling of the amount the second rotating board is driven can be accurately carried out.